A Year Lond Study: Bare Topsoil Temporal and Vertical Variability in Hydraulic Properties

Soils exhibit considerable variability in their physical and hydraulic properties, which can change both spatially and temporally. Research on the temporal variability and especially the internal variability of hydraulic and physical properties within the shallow topsoil itself remains scarce. In this one-year study (2023–2024), we investigated seasonal changes in the physical and hydraulic properties of post-tillage bare topsoil at the plot scale, hypothesizing significant temporal variability and heterogeneity within topsoil. The study was conducted in Czechia in a continental humid climate on agricultural soils. Monthly sampling was carried out on a 16 m² plot during the growing season, focusing on the 12 cm thick topsoil layer, which was divided into the upper section (0–5 cm) and the deeper section (7–12 cm). A total of 28 disturbed and 107 undisturbed samples were collected, 40 soil water retention curves (SWRC) were measured. Robust statistical analyses were performed, including normality tests (Shapiro-Wilk, Kolmogorov-Smirnov, Anderson-Darling, and Lilliefors tests) and variability tests (Kruskal-Wallis, Dunn test, LOWESS, and MANOVA). The results revealed a . For instance, the overall mean of the n parameter in the upper section was 1.404 ± 0.126, exhibiting greater variability compared to the deeper section, which had a mean of 1.254 ± 0.103. The mean α parameter showed similar overall variability in the deeper section (0.075 ± 0.024) and the upper section (0.060 ± 0.019). The contrasting patterns of variability highlight the importance of thoroughly evaluating both datasets. Relying solely on statistical results of the van Genuchten parameters or the SWRC data alone risks overlooking important temporal and vertical variations, emphasizing the need for comprehensive analyses.